It is reported that catechins have effects, for example, as an inhibitor against a rise in cholesterol level (Japanese Patent Application Laid-Open (kokai) No. Sho 60156614), for reduction of a plasma cholesterol level (Japanese Patent Application Laid-Open (kokai) No. Hei 6-80580) or as an α-amylase activity inhibitor (Japanese Patent Application Laid-Open (kokai) No. Hei 3-133928). This suggests that tea beverages such as green tea, black tea and Oolong tea have physiological effects.
In order to gain such physiological effects of catechins, an adult must take four to five cups of tea a day (The Food Industry, 35(14), 26-30(1992)). There has accordingly been a demand for the development of a technique of mixing a high concentration of catechins in a beverage. Tea beverages containing a high concentration of catechins (Japanese Language Laid-Open Publication (PCT) No. Hei 11-504224, Japanese Patent Application Laid-Open (kokai) No. 2000-60427) have however strong bitterness and astringency due to catechins, caffeine and tannin extracted from tea (tea leaves) so that they are not preferred as a beverage.
As a conventional evaluation method of bitterness, known is a method using quinine sulfate. According to an index as specified by the bitterness evaluating method by using sulfate quinine (Equivalency Concentration Testing Method/Organoleptic Test Handbook, ed. by Organoleptic Test Committee/JUSE, published by JUSE Press, Ltd.), beverages having an index of 5 or greater are not suited for drinking owing to intense bitterness. With regards to beverages having various catechin concentrations, an index of those having a catechin concentration of 300 mg/500 mL exceeds 6, while those having a catechin concentration of 900 mg/500 mL exhibits an index of 10 or greater and in addition, has pungency.
A beverage increased in its catechin content to impart it with physiological usefulness has accordingly strong bitterness and astringency and is not suited for daily drinking.
As an agent for reducing this bitterness and astringency peculiar to catechins, proposed are a cyclodextrin (Japanese Patent Application Laid-Open (kokai) No. Hei 10-4919) and a bitterness reducing agent comprising a natural polymer (Japanese Patent Application Laid-Open (kokai) No. Hei 3-164136, Japanese Journal of Taste and Smell Research, 6(3), 665-668, 1999). The physiological action of catechins can be exhibited effectively by increasing their intake amount. Beverages containing much catechins are inferior in taste, but forms facilitating high intake of catechins is desired from marketability.
As a method for incorporating a large amount of catechins in a beverage, proposed is a method of adding powdered tea leaves (Japanese Patent Application Laid-Open (kokai) No. Hei 10-234301). In this method, however, when powdered leaves are added at a high concentration, excessive existence of powders in the beverage disturbs smooth throat-feel and leaves an uncomfortable taste in the mouth. In addition, such a beverage provided after a distribution process have precipitates of powdered tea leaves on the bottom of its container or their floats on the surface of the beverage upon drinking. Such precipitates in a transparent container, for example, PET bottle greatly damages its appearance and hence commodity value. Moreover, in a beverage providing physiological effects, consumers must shake or stir it upon drinking to disperse the powdered tea leaves uniformly.
A method of adding catechins in the dissolved form by making use of a catechin preparation is proposed (Japanese Patent Application Laid-Open (kokai) No. Hei 2-182176, Japanese Language Laid-Open (PCT) No. Hei 8-504591). The dissolved catechins have bitterness and astringency. A beverage containing a large amount of them has therefore intense bitterness and astringency and drinking of such a beverage is rather a pain. Accordingly, daily or continuous drinking until its physiological effects appear is impossible.
An object of the present invention is therefore to provide a beverage containing a high concentration of catechins but having improved taste with reduced bitterness and astringency.